Trebek shared the news on YouTube, telling his fans, "I have some news to share with all of you and it’s in keeping with my longtime policy of being open and transparent with our 'Jeopardy!' fan base."

"Now, just like 50,000 other people in the United States each year, this week I was diagnosed with stage 4 pancreatic cancer. Now normally, the prognosis for this is not very encouraging, but I’m going to fight this, and I’m going to keep working," he added. "And with the love and support of my family and friends and with the help of your prayers also, I plan to beat the low survival rate statistics for this disease."

In classic Trebek fashion, he closed the video with wit and humor, saying, "Truth told, I have to! Because under the terms of my contract, I have to host 'Jeopardy!' for three more years! So help me. Keep the faith and we’ll win. We’ll get it done."

The 78-year-old has been the host of "Jeopardy" since 1984 and is currently in his 35th season fronting the popular quiz show.

He took the job at "Jeopardy" after almost two decades hosting other game shows in his native Canada and in the U.S. with programs like "Jackpot," "High Rollers" and "The $128,000 Question."

The Washington Post via Getty Images, FILE

Alex Trebek poses on the set of his game show, "Jeopardy," April 21, 2012, during a special taping in Washington, D.C.

Trebek took a leave of absence from the show last year after he underwent brain surgery for a subdural hematoma, which is blood clots on the brain.

Celebrities and members of the "Jeopardy!" community, including star Ken Jennings, posted well-wishes and messages of support on social media.

The Sajak family is deeply saddened to hear of Alex Trebek’s struggle with cancer. Our hearts go out to him and his family. But there is no one I know who is stronger and more determined, and I would never bet against him. We, and the entire country, are pulling for you, Alex.